The present invention is directed to electromagnetic antennas, and especially to electromagnetic antennas employing a plurality of antenna elements known as patch antenna elements. Such patch antenna construction is advantageous in constructing antennas that are known as steerable beam antennas. Steerable beam antennas employ fixed antenna elements, such as patch antenna elements, to xe2x80x9csteerxe2x80x9d loci of sensitivity (i.e., transmitting beams or bearings of reception) by establishing predetermined interference patterns among the various patch antenna elements. The desired predetermined interference patterns are commonly effected by imposing phase differences among the various patch antenna elements.
It is desirable that patch antenna elements in steerable beam antennas be closely or densely situated in order that maximum interaction among the various patch antenna elements may be realized. Prior art coupling structures employed for coupling the respective patch antenna elements with a signal coupling locus (e.g., a transmission line leading to a host device such as a transceiver for radio or radar operations) have heretofore occupied an undesirable lateral expanse about the respective antenna patch elements. As a result, antenna patch elements have not been as densely situated as desired. One solution has been to provide larger antenna patch elements. Installing an antenna patch element that occupies a larger area provides a larger expanse in the vicinity of that patch element for effecting the requisite electromagnetic coupling. However, the larger the respective patch elements, the less resolution that can be established in steering beam operations. That is, larger patch elements yield coarser beam patterns that result in coarser control of beam steering operations.
Another desired feature for an antenna device, such as a steerable beam antenna, is that electromagnetic signals transferred between the various antenna patch elements and a signal coupling locus be of equal strength. That is, it is desired that the structure or device that effects the desired distribution does not itself impart a variance to the signals being distributed.
There is a need for a waveguide apparatus for distributing arrays of small antenna patch elements and does not itself impart a variance to the electromagnetic signals being distributed.
While such an apparatus is particularly useful for steerable beam antennas using closely arranged antenna patch elements, the apparatus has utility in other antenna coupling structures and arrangements. The invention disclosed, described and claimed herein is not limited to steerable beam antenna devices.
A waveguide apparatus for bidirectional distribution of signals includes: (a) a first conductive element parallel with a reference plane; (b) a second conductive element in spaced parallel relation with the first element; (c) a first coupling locus situated in the first element; and (d) second coupling loci arrayed in the second element. Each second coupling locus includes an aperture traversing the second element at a lineal distance from the first coupling locus in a lineal plane perpendicular with the reference plane and containing a line from the first coupling locus. Each aperture has a major and a minor axis. The major axis establishes an installation attitude with respect to the lineal plane. The lineal distance and the installation attitude for each aperture are selected to distribute electromagnetic signals having substantially equal power.
It is, therefore, an object of the present invention to provide a waveguide apparatus for distributing electromagnetic signals within an antenna device that permits closely arranged arrays of small antenna patch elements and does not itself impart a variance to the electromagnetic signals being distributed.